The present invention relates to a device wherein the hydraulic retarder used for the large-sized vehicles such as buses, trucks, etc. and the parking brake are united to aim at the compactification and the space-saving.
Usually, there are three kinds of braking devices for cars, routine brake, parking brake and deceleration brake, depending on the purpose for use. Thereamong, the routine brake is a treadle brake and is used for deceleration and stopping of vehicle by braking whole wheels simultaneously. The parking brake is a manual brake and there are a type to work the same device as the routine brake for rear wheels through an auxiliary working mechanism and a mechanical center brake used for parking by fitting to the transmission or the propeller shaft, which can also serve as an assistance at the time of the breakdown of the routine brake and for stopping vehicle at the time of emergency.
For such parking brake, duo-servo type drum brake is used generally, wherein two brake shoes each laminated with a lining on an arcuate member are connected through a link inside a brake drum rotatable unitedly with a wheel axle and, by operating the parking lever, these shoes are pressed against the brake drum to stop the rotation of the axle.
Moreover, the decelerating device is to be used for large-sized trucks and buses. It is used because of being in danger of the lowering in the performance of brake due to the heat generation at the friction portions of brake with the routine brake alone when decending a long slope, and there are exhaustion brake, hydraulic retarder, electromagnetic retarder, etc. Thereamong, the hydraulic retarder (hereinafter referred to as retarder simply) shows a preferable characteristic as a decelerating device that the absorbing horsepower increases abruptly with an increase in the number of revolutions and is assembled most frequently into the transmission or the driving device of rear wheels.
The body of said retarder is so constructed, as shown in FIG. 8, that a plurality of rotor vanes (52) fixed radially making the axle (51) as a center and rotating unitedly with the axle (51) and a cylindrical vane chamber (54) provided in a ring form around the axle (51) by means of a case of vane chamber (53) surrounded said vanes (52) are provided, and, inside said vane chamber (54), stator vanes (55) fixed to the case of vane chamber (53) in opposition to a plurality of rotor vanes (52) are formed. When working the retarder, cooling oil is supplied to the oppositely facing space between the rotor vanes (52) in the vane chamber (54) and the stator vanes (55), thereby the energy of rotating rotor vanes (52) is transmitted to the circulating cooling oil as a heat to have the deceleration.
As described, the hydraulic retarder and the parking brake have been constructed conventionally as quite different devices despite being same braking devices. Since this is disadvantageous spatially, it has been earnestly desired to aim at the space-saving by constructing them unitedly. Furthermore, although the control of the working of hydraulic retarder has been performed conventionally through the flow rate of cooling oil supplied to the vane chamber, that is, the level of oil surface, the level-controlling device for oil surface is very expensive and yet heavy in weight. Therefore, a simple method has been sought. The purpose of the invention is to provide a hydraulic retarder with parking brake possible to dissolve the problems aforementioned at a stroke.